Prejunctional and postjunctional effects of tubocurarine and pancuronium in man

The effects of small doses of tubocurarine and pancuronium on peak tetanic tension and tetanic maintenance were compared. Forty patients undergoing elective orthopaedic procedures under general anaesthesia were studied. Changes in neuromuscular transmission were measured by recording the isometric contraction of the adductor pollicis muscle evoked by supramaximal stimulation of the ulnar nerve at the wrist. Small doses of pancuronium affected predominantly the peak tetanic tension, while small doses of tubocurarine affected mainly tetanic maintenance. Thus, different degrees of depression of peak tetanic tension and tetanic maintenance were observed with tubocurarine and pancuronium. This clinical study supports Bowman's hypothesis, based upon laboratory findings in the cat, that prejunctional and postjunctional effects of neuromuscular blocking agents depend on their affinity for cholinoceptors at different sites.